It is common practice when constructing buildings to connect a water supply line to a network of pipes that will deliver cold and hot water flow to various faucets and to one or more water heaters and water treatment devices.
The network of pipes is typically constructed using segments of metallic pipe which are usually affixed to wooden floor joists under the lowest level flooring.
It is common for pipe segments to be joined using straight and angular couplings which are then soldered in place to establish cohesion and leak proofing.
The segments thus joined are usually affixed to the wooden floor joists using some type of mounting fixture.
The mounting fixtures are designed to hold the pipe against the floor joists using metallic screw hardware.
The nature of such mounting fixtures is that when applied, the pipe is pressed up against the floor joists making soldering at that point risky because of the proximity to the wood. As a result, the pipe segments are typically joined and soldered at ground level, while well below the wooden joists, and only later affixed to the joists.